US 6,142,627 A · Short-corridor progressive lens

Abstract

A progressive ophthalmic lens designed for use in eyeglass frames having a vertical ("B") dimension <36 mm is presented. The lens features a short (nominally 13-14.5 mm) progressive corridor and a novel treatment of the progressive optics that compensates for the distortion effects, i.e., astigmatism, that would otherwise result from the compression of the optics into a smaller than usual area. That includes (1) permitting a small amount of the astigmatic aberration to extend into the peripheral zones of the distance portion above the distance fitting center, with 0.50 D isocurves of surface astigmatism forming an included angle of about 110.degree., (2) defining a circle of 30 mm diameter centered 2 mm vertically below the distance fitting center in which the maximum value of unwanted astigmatism does not exceed the add value of the lens plus 0.25 D, (3) distributing astigmatism so that the isocurves from D.sub.1 to D.sub.2 on upward arcs (3,4) of the 30 mm circle adjacent the reading zone are much more closely spaced than the isocurves from D.sub.1 to D.sub.2 on downward arcs (1,2) of the 30 mm circle from the distance zone (where ##EQU1## where .DELTA.P is the add value of the lens), and (4) establishing a value .rho. of from 2.7-5 for the ratio of the magnitude of the gradient of astigmatism over the combined lengths of arcs 3 and 4 to the magnitude of the gradient of astigmatism over the combined lengths of arcs 1 and 2. Examples of preferred embodiments are presented having continuous and discontinuous meridional power laws.

Claims21

Dependent claims

A progressive power ophthalmic lens having:

a distance zone;
a distance fitting center;
a near zone having a reading portion;
an intermediate zone having a short progressive corridor;
and
an astigmatism relationship, .rho., of at least 2.7
where
.rho.=<.nu.>.sub.3+4 /<.nu.>.sub.1+2,
and where <.nu.>.sub.1+2 is the gradient of surface astigmatism of the lens between diopter magnitudes D.sub.1 and D.sub.2 averaged over first and second arcs of a circle of 30 mm diameter superimposed on the lens and centered 2 mm directly below the distance fitting center of the lens,
and where <.nu.>.sub.3+4 is the gradient of surface astigmatism of the lens between diopter magnitudes D.sub.1 and D.sub.2 averaged over third and fourth arcs of a circle of 30 mm diameter superimposed on the lens and centered 2 mm directly below the distance fitting center of the lens,
said third and fourth arcs being in the lower hemispheres of said circle and being on opposite sides of said reading portion;
and
said first and second arcs being above said third and fourth arcs and being in regions of surface astigmatism of about 0.5 D or greater.

10 more elements

A progressive power ophthalmic lens having:

a distance zone;
a distance fitting center;
a near zone having a reading portion;
an intermediate zone having a short progressive corridor;
and
an astigmatism relationship, .rho., of at least 2.7
where
.rho.=<.nu.>.sub.3+4 /<.nu.>.sub.1+2,
and where <.nu.>.sub.1+2 is the gradient of surface astigmatism of the lens averaged over first and second arcs of a circle of 30 mm diameter superimposed on the lens and centered 2 mm directly below the distance fitting center of the lens,
and where <.nu.>.sub.3+4 is the gradient of surface astigmatism of the lens averaged over third and fourth arcs of a circle of 30 mm diameter superimposed on the lens and centered 2 mm directly below the distance fitting center of the lens;
said third and fourth arcs being in the lower hemispheres of said circle and being on opposite sides of said reading portion;
said first and second arcs being above said third and fourth arcs;
said progressive corridor continuously increasing in power from said distance portion toward said reading portion and having a discontinuous step of from 0.25 diopters to 0.75 diopters at the end of said corridor adjacent said reading portion;
said step of 0.25 D-0.75 D resulting in a surface discontinuity blended into the surface of the lens between arcs of first and second circles of different diameters, said arcs being tangent to each other at a point on the centerline of said progressive corridor and at the end of the corridor at the reading portion, and said arcs extending outwardly and downwardly from said point of tangency.

11 more elements

A progressive power ophthalmic lens having:

a distance zone;
a distance fitting center;
a near zone having a reading portion;
an intermediate zone having a short progressive corridor;
and
a surface astigmatism relationship, .rho., having minimum values corresponding to add power of the lens as follows:
______________________________________ Add 1.00 1.25 1.50 1.75 2.00 2.25 2.50 2.75 3.00 .rho. 5.0 3.7 4.0 4.2 4.1 3.6 3.7 3.5 3.0 ______________________________________
where
.rho.=<.nu.>.sub.3+4 /<.nu.>.sub.1+2,
and where <.nu.>.sub.1+2 is the gradient of surface astigmatism averaged over first and second arcs of a circle 30 mm in diameter superimposed on the lens and centered 2 mm directly below the distance fitting center of the lens,
and where <.nu.>.sub.3+4 is the gradient of surface astigmatism averaged over third and fourth arcs of a circle 30 mm in diameter superimposed on the lens and centered 2 mm directly below the distance fitting center of the lens,
said first, second, third and fourth arcs extending between isocurves of surface astigmatism of diopter magnitude D.sub.1 and D.sub.2, where ##EQU5## where .DELTA.P is the addition value for the lens.

9 more elements

Dependencies are inferred from the claim text.

Short-corridor progressive lens

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Short-corridor progressive lens

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Abstract

Claims21